4718723 Original Excavator Stopper for Hitachi ZX300-5A ZX330-5G ZX330-5A

Part number 4718723 is the official part number for the hydraulic pump regulator and stopper of Hitachi's original excavator. This component is a key mechanical limit and positioning part in the variable adjustment mechanism of the hydraulic main pump. It is usually installed inside the regulator of the main pump and works in conjunction with servo plungers, feedback rods, and other parts to accurately limit the maximum or minimum angle of the inclined plate, thereby controlling the displacement and output flow of the pump. It is the core mechanical limit component that ensures the matching of engine power and hydraulic load, and achieves high efficiency and energy saving. As an original standard component, it is mainly suitable for the main hydraulic pump used in Hitachi's various medium and large hydraulic excavators, commonly found in models such as ZX200-3, ZX240-3, ZX270-3, ZX330-3, ZX350-3, ZX360-5, etc

This original stopper belongs to the precision mechanical limit device in the hydraulic pump variable adjustment mechanism. Its core function is to provide a rigid and precise mechanical stop point inside the regulator, which limits the limit position of the inclined plate swing through contact with moving parts such as connecting rods or servo plungers, ensuring that the flow rate variation range of the pump is always within the designed safe and efficient range. It is usually made of high-strength alloy steel (such as bearing steel or alloy tool steel), which undergoes precision machining, heat treatment (such as quenching and tempering), and surface hardening treatment (such as nitriding or chrome plating), and has extremely high hardness, wear resistance, and impact toughness.

The maintenance core of this stopper lies in regularly checking its wear condition, installation firmness, and integrity of the contact surface. Regular inspection: Usually conducted during major repairs, disassembly, or abnormal flow control of hydraulic pumps. Symptom of malfunction: If the hydraulic system experiences unstable pump output flow, slow and fast movements, engine stalling or abnormal noise during heavy loads (especially metal knocking inside the regulator), after ruling out other reasons, it is necessary to consider whether the misalignment of the inclined plate limit is caused by wear, displacement or damage of the stopper. Once the stopper is found to be damaged, it must be replaced with a new original part and cannot be continued to be used. Daily maintenance should ensure the cleanliness of hydraulic oil to prevent impurities from entering the pump and exacerbating wear.